Apparatus for making sheet glass



Aprilf19, 1938. w. G. KoUPAL ET AL 2,114,715

APPARATUS Foa MAKING SHEET GLASS Filed Jan. 11, 195e s sheets-sheet 1INV/moles hours/QG Kom/Pnl.. "'va Hann Y/ H1 rnc-R A TORNEYS.

' April 19, 1938. WIG. KouPAl. ET Al. 2,114,715

APPARATUS FOR MAKING SHEET GLASS Filed Jan. ll, 1936 3 Sheets-Sheet 2 INVEN TORS WFM-ran G. Koupna.

Hnkva rf." H1 TNF@ April 19, 19.38. w, G. KCUPAL ET AL APPARATUS FORMAKING SHEET GLASS Filed Jan. 11, 195s s sheets-sheet s Fly/.4.

Y IN V EN TORS WHL. T542 G Ko upf. Q- BY Hamer FT' Hf rye-R 7' ,4rToRNEYS.

Patented Apr. 19, 1938 UNITED y STAT-Es 2,114,715 `PATENT OFFICE2,114,715 APPARATUS FOB. MAKING SHEET GLASS Walter G. Koupal, Tarentum,

Bitner, Oakmont, Pa., Plate Glass Company,

. Sylvania and Harry Fr assignors to Pittsburgh a corporation of Penn-Application January 11, 1936, Serial No.4 58,714 5 claims.' (c1. 49 '17)The invention 'relates to apparatus for making sheet glass by acontinuous process, wherein the sheet is drawn vertically from a moltenbath. In an operation of this kind, the edges of the sheet lierelatively close to the side walls of the tank and great diiiiculty isexperienced in maintaining the glass in the bath at the points fromwhich the sheet edges are generated in condition forsatisfactory drawingover extended periods of time. It is necessary to lower the temperatureof the glass for the edge gather to" a point at which the viscosity willbe high enough to maintain sheet width, but this condition is difiicultto keep localized and the chilled portion extends to a width and depthbeyond that'immediately feeding into the edge with the result that thisportion gets too cold and stiff. lThe edge portion of vthe sheet isimperfe'ctly formed as to 'i thickness and straightness and' in additionvents voccur in the bead. These defects cause much breakage inthemachines, and even with no breakage, a narrower net sheet results beforeproper sheet strength'or thickness is established from the edge intoward the sheet center. The excess chilled portion devitrifles alongthe side of the drawing kiln adjacent to the edge of.

the sheet and also on the ends of the draw bar.

This development causes periodical shut downs for reheating and'considerable production is lost. Were it not for heating up the edges,the kiln cycleswould be practically indenite as regards the condition ofthe kiln itself.

I t is the object of the present. invention to overcome the foregoingdifficulties and provide means (subject to regulation to meet varyingconditions), which will maintain the molten glass in the areas fromwhich the edges of the sheet are drawn at the same temperature as long-as the drawing operation is continued, thus givingedges 'which areuniform in thickness; straight, and free from vents, and Awhich preventsdevitrication and avoids the necessity of the accompany#- ing periodicshut `downs for reheating.v Certain embodiments of the invention areillustrated in the accompanying drawings, wherein:

Figure 1 is a longitudinal section drawing kiln or tank equipped withthe improvement.- Fig. 2.is a partial plan view. Fig. 3 is a section onthe lineIII-III of Fig. 2. Figs. 4, 5

and 6 illustrate a modification, Fig. 4 being a plan View, Fig. 5 asection on the line V-V of Fig. 4, and Fig. .6 an end view. And Figs. 'lvand 8 illustrate a further modification, Fig. 7 being a plan, 'and Fig.8 a vertical section. -Y

Referring to the drawings, and particularly to Fig.` 1, which shows theing .tank or `-kiln of substantial depth connected at its left hand endwith al melting tank of the usual construction, -2 being the endv wallof such melting tank. Lying above the kiln I is a cover Ssheets passtherethrough and through a' y upon the tank rods I2, the rods clay work,I is the drawor roof made up of thearch members 3 and and the L blocks5, 5, suitably supported byl means which are not shown. Extendingtransversely of the tank between the side walls 6, 6 is a draw bar 'lwhosecenter line deiines the line of generation of the glass sheet 8which is,'

drawn continuously' from the bath. As 'illuse trated, the drawing isaccomplished through a leer of the Fourcault type comprising` a casing'9 provided on its interior with pairs of ppposing driven rolls whichgrip the faces of the glass sheet, such drawing mechanism being wellknown in the art and requiring no further description or illustration.

`Suitably supported from the side. walls 6, 6 of the tank on brackets Ibrare the edge bowls .'Ia,`1a of the type shown inthe Slinglu Patentvsealed at each end and submerged in the glass. 'Ihe composition of theseascoloy, which is a` nickel `chromium iron alloy, but any suitable alloymay be employed which will not discolor the glass under the temperatureconditions encountered, various nickel chro'' I mium alloys beingsuitable for this purpose. 'Ihe electrodes arefpreferably located about4 inches out'from the side wall of the tank and are about 14 inchesapart, althoughthese dimensions-are subject to variations depending uponconditions. Eachv electrode is sup rted from a plate II. lying wall,connection being made b e`- and electrodes by means of the being securedto the plates and electrodes bywelding. The electrode, rod and plate maybe all of the sa'me composition or may be made of differentcompositions. The plates tween' the plates II, I I have attached totheir ends theleads I3, I3

electrodes is preferably drawing-apparatus. Located at isa pair ofelectrodes- IIJ,4 I0, such electrodes as illustrated in Figs..1, 2 and3,. consisting of short lengths of tubing connected toa suitable sourceof current supply.

In order to hold the plates II., I'I securely in Y' position upon thewall of the tank, blocks I4, I4 of refractory material, such .as clay,are placed thereon and by their weight perform the desired function,thejblocks I4, I4 also serving to iit up againstgthe ends of the Lblocks and close t e cracks or spaces between the ends of the .L blocksand the side walls of the furnace, thus reducing the infiltration of airat these points.

In theoperation of the apparatus, there is a.

y tendency for the glass beneath the edge bowl, from which the edge ofthe sheet is generated, to

gradually cool down and become too viscous, as heretofore pointed out,which results in imperfections in such edges and breakage. It alsoresults in devitrification along the side edges of the drawing kiln andfrom time to time periodic shut downs for reheating are required.Thefuse of the electrodes I0, I0 with the ow oi' .current therebetweenthrough the glass largely overcomes this difficulty, as this flow ofcurrent heatsv the glass to any Adesired extent, this being subject toregulation so as to secure exactly the right degree of heating, as toomuch heating would render the glass unduly fluid. It is thus lpossibleto maintain a very uniform condition at the point at which the sheetedge is generated, which results in a more perfectedge and one which isnot -subject to breakage due to vents and the like. The heating of theglass at this point also prevents devitrification, so that the drawingoperation may be continued-for indefinite periods-without shutting downto recondition thel glass next to the side walls of the tank.

It will be understood that the shape and the vlocation of `theelectrodes may be modified to a s0 large extent without departing fromthe inventhe same as in the construction heretofore d e-v tion, andFigs. 4, 5 and 6 illustrate a modification involving a very considerabledeparture,I but one` which has been found to operate successfully. Thegeneral arrangement of the tank parts is scribed, the .departure in themodification relating to the shape and location of the electrodes. Inthis case, the electrodes comprise the pair of flat plates I5, I5 ofnickel chromium or other 4o suitable alloy having theirupper'portionsbent at right angles to their vertical portions so that they Alie uponthe top wall of the tank, suchtop portions being connected to suitableleads I6, II for supplying current.

are employed in this construction and correspond in function to that ofthe blocks I4, I4 of the first construction. In this case, theelectrodes I5, yI5 llie against the face of the side wall 6 instead ofbeing spaced away therefrom as' in the rst type of construction.

In the modification of Figs. 7 and 8, the electrodes 20 are of angularshape and are provided with shanks I9 lying above the wall 6. With thisform of electrode, the principal current flow is between the portionsmost remote from the wall 6 where the glass is hotter than it is nextto:

the wall and of lower resistance, but at the same time there issufficient heating 'effect next to the wall to keep the glass duid andprevent devitriflcation. By tilting lthe electrodes as indicated at A ofthe bath from which -edges of the sheet are drawn and the other to therear thereof, andi drawn comprising a pair of electrodes in the glass ateach side of the kiln, the members of each pair being spaced apart withone member of each pair in front ofthe area cfrom which the edge isHolding down blocks I8, IB

means for causing a flow of electric current through the glass from onemember of each pair of electrodes to the other member of the same pair.

2. In combination with a drawing kiln adapted to carry a body of moltenglass and means for drawing a glass sheet continuously therefrom withits edges adjacent the side walls of the kiln, means for applying heatto those portions only of the bath from which edges of the sheet aredrawn comprising a pair of electrodes in the glass at each side of thekiln, the members of each pair being spaced apart with one member -ofeach pair in front of the area from which the edge is drawn and theother to the rear thereof, and means for causing a flow of electriccurrent through the glass from one member of each pair of electrodes tothe other member of the same pair, said electrodes comprising verticalmembers spaced inward from the walls of the kiln.

3. In combination with ,a drawing kiln adapted to carry a body of moltenglass and means for drawing a vglass sheet continuously therefrom withits edges adjacent the side walls of the kiln, means for applying heatto those portions only of the bath from which edges of the sheet aredrawn comprising a pair of electrodes in the 'glass at each side of thekiln, the members'of each pair being spaced apart with one member ofeach pair in front of the area from which the edge is drawn and theother to the rear thereof, and means for causing a flow of electriccurrent through the glass from one member of each pair of electrodes tothe other member of the same pair, said electrodes comprising verticalplates lying against the wall of the tank.

4. In combination with a drawing kiln adapt- 'ed to carry a body ofmolten glass, means for drawing a glass sheet from said body with thesheet extending transversely of the kiln with its edges adjacent theside walls thereof, and edge holding means for the sheet at each side ofthe kiln above the surface of the molten body, means for applying heatto those portions only of the bath from which edges of the sheet aredrawn comprising a pair of electrodes in the glass at each side of thekiln, the members of each pair beingspaced apart with one member of eachpair in front of the area from which the edge is drawn and the other tothe rear thereofl and means for causing a flow of electric currentthrough the glass from one member of each pair with its edges adjacentthe side walls of the kiln, means for applying heat to those portionsonly of the bath from which edges of the sheet are drawn comprising apair of electrodes in the glass at veach side of the kiln, the membersof each pair being spaced apart with one member of each pair in front ofthe area from which the edge is drawn and the other to the rear thereof,-and means for causing a flow of electric current through the glass fromone'member of each pair of electrodes to the other member of the samepair. said electrodes being in the form of angles having their verticallegs next to the tank wall and their horizontal lips extending awaylfrom the wall below the-surface of the glass. f, v

WALTER G. KOUPAL. HARRY E. m'rNER.

